1. Field of the Invention
The present invention relates to a pressure plate subassembly for a multidisk friction clutch including a housing which is connectable or connected to an abutment arrangement for joint rotation about an axis of rotation, a pressure plate arranged in the housing so that the pressure plate is rotatable together with the housing and axially displaceable relative to the housing relative to the axis of rotation, and a force accumulator for generating a pressure force, the force accumulator being supported or supportable on the housing and on the pressure plate.
2. Description of the Related Art
German reference DE 195 45 972 A1 discloses a multidisk friction clutch in which a plurality of clutch disks are designed in the form of lamellae connected to a common hub part. A pressure plate capable of being loaded by a force accumulator is provided in the clutch housing. Furthermore, a plurality of intermediate disks are connected fixedly in terms of rotation to the clutch housing, these intermediate disks in each case engaging between two lamellae of the clutch disks. The intermediate disks and the lamellae are capable of being pressed against one another by the force accumulator to generate mutual frictional bearing contact. The force accumulator is designed in the form of a diaphragm spring and lies within the housing essentially parallel to a housing bottom such that the diaphragm spring may be supported on the housing and on the pressure plate to generates the necessary pressure force on the pressure plate to effect the frictional bearing contact.
In friction clutches of this type, there is a problem that the supply of cooling air into the interior of the clutch is limited, with the result that overheating of the clutch may occur, at least when the clutch is operated for a relatively long time with slip.
Furthermore, in this known friction clutch, there is the problem that sufficient construction space for the pivoting movement of the force accumulator must be provided in the housing itself to allow the greatest possible lift-off travel.
The object of the present invention is to provide a pressure plate subassembly for a friction clutch including an improved supply of cooling air to the components of the friction clutch which are heated during operation and a reduction in the overall available construction space.
According to an embodiment of the present invention, the object is achieved by a pressure plate subassembly for a multidisk friction clutch comprising a housing which is connectable or connected to an abutment arrangement for joint rotation about an axis of rotation, a pressure plate operatively arranged in the housing for rotation with the housing about the axis of rotation and for axial displacement relative to the housing in the direction of the axis of rotation, and a force accumulator for generating a pressure force arranged so that it is supported or supportable on the housing and on the pressure plate.
In the clutch according to the present invention, the force accumulator is arranged outside the housing.
The measure of arranging the force accumulator outside the housing of the pressure plate subassembly markedly reduces the overall size of the clutch which is determined essentially by the size of the housing. The maximum lift-off travel of the pressure plate may be defined by stops formed in the housing itself. When the pressure plate butts against these stops, the force accumulator may be further loaded without an enormous increase in force such as, for example, by pedal actuation. Accordingly, the construction space allowing for this further loading of the force accumulator does not have to be provided within the housing. Moreover, arranging the force accumulator outside the housing affords the possibility in a simple way of guiding cooling air, without it being impeded by the force accumulator, through the housing to the pressure plate and to other components arranged in the housing.
The force accumulator may, for example, be arranged on a side of the housing which faces away from the pressure plate.
To simplify the interaction between the force accumulator and the pressure plate, the pressure plate comprises at least one force accumulator support region which passes through an orifice in the housing and on which the force accumulator can act.
It is noted here, that the statement that the force accumulator is supported on the housing and on the pressure plate in corresponding regions does not necessarily mean the direct physical contact of the force accumulator with these components. Rather, support may be effected either directly, that is to say without any components being interposed, or indirectly, that is to say by the inclusion of the force transmission function of various components in the force transmission from the force accumulator to the pressure plate and/or from the force accumulator to the housing.
If the at least one force accumulator support region includes a surface region running obliquely and/or in a contoured manner relative to a radial direction and a circumferential direction, then care is taken to ensure that, in the rotational mode, air is conveyed into the inner regions by this obliquely running surface resembling a turbine blade and then contributes, for example, to cooling the pressure plate.
To reinforce this conveying effect and to ensure that the pressure plate is loaded as uniformly as possible, a plurality of force accumulator support regions succeeding one another in the circumferential direction are arranged on the pressure plate.
When the pressure plate subassembly according to the present invention is used in a friction clutch with a clutch disk provided with friction linings, the friction linings may become abraded during slippage. The abrasion, i.e., wear of the friction linings, causes the pressure plate and the force accumulator become displaced. To avoid changes in the operating characteristics, in particular the force characteristic of the force accumulator, which are induced by displacements of this nature, it is possible to provide a wear-compensation arrangement to automatically compensate for wear which occurs during operation.
The wear-compensation arrangement may comprise a wear-adjustment device arranged in the support path between the force accumulator and the pressure plate and/or in the support path between the force accumulator and the housing. The wear-adjustment device includes at least one wear-adjustment element which can be displaced to compensate for wear. Furthermore, the wear-adjustment device also includes at least one blocking/detection element with a blocking section that is preloaded against the wear-adjustment device and acts on this device to prevent movement of the at least one wear-adjustment element and a detection section which interacts with or is made to interact with a component whose position can be affected in the event of wear to detect the level of wear. In response to wear, the at least one blocking/detection element is moved counter to its preloading into a position in which the at least one wear-adjustment element is released.
To ensure that the automatic wear compensation occurs during the next clutch release operation, a locking element is arranged for locking the blocking/detection element against movement in its preloading direction once the at least one blocking/detection element has been moved into this position. For this purpose, the at least one locking element may comprise a locking slide element, preferably a locking wedge element, which is preloaded to move in a locking direction.
In the pressure plate subassembly according to the present invention, the wear-adjustment device may be arranged between the force accumulator and the at least one support region. The at least one locking element may then also be supported on at least one support region.
To obtain rotational coupling between the pressure plate and the housing, the pressure plate may comprise at least one rotational coupling projection which extends essentially radially outward and which engages displaceably in the direction of the axis of rotation and with a first circumferential direction movement play in a rotational coupling recess formed in the housing. After a relatively long service life, material wear may cause the at least one rotational coupling projection to dig at least slightly into the housing material surrounding the rotational coupling recess. If this occurs, the pressure plate will be fixed by a shoulder region formed on the housing and will not release the friction linings of the clutch disk during the clutch disengagement operation. To avoid this detrimental effect, a return arrangement is provided by for bringing the at least one rotational coupling projection into a position relative to the rotational coupling recess in which there is essentially no mutual bearing contact between the at least one rotational coupling projection and the housing.
The return arrangement may include at least one return projection on the pressure plate which extends essentially radially outward and which engages displaceably in the direction of the axis of rotation and with a second circumferential direction movement play into a return recess formed in the housing. Furthermore, at least one return force generating element is arranged between the at least one return projection and the housing for prestressing the at least one return projection and/or the at least one rotational coupling projection into a preferably essentially central position relative to the circumferential direction, in the return recess or rotational coupling recess. Furthermore, the first circumferential direction movement play is preferably smaller than the second circumferential direction movement play.
To generate a suitable return force irrespective of the direction of relative rotation, at least one spring element supported relative to the housing and to the return projection is arranged in each case on the two circumferential sides of the at least one return projection. The at least one spring element preferably comprises a tube spring element.
The pressure plate subassembly according to the invention is particularly suitable for use in multidisk clutches. For this purpose, there may be provision for arranging in the housing, at an axial distance from the pressure plate, at least one intermediate plate which is axially displaceable relative to the housing and is rotatable together with the latter about the axis of rotation.
So that the rotational coupling of the intermediate plate to the housing may be effected in a simple way, the at least one intermediate plate may have at least one rotational coupling projection which extends essentially radially outward and which engages displaceably in the direction of the axis of rotation and with a first circumferential direction movement play into a rotational coupling recess formed in the housing.
The intermediate plate may also have a return arrangement which is the same as the return arrangement used for the pressure plate. In the return arrangement for the intermediate plate, the at least one rotational coupling projection is capable of being brought, relative to the rotational coupling recess, into a position in which there is essentially no mutual bearing contact between the at least one rotational coupling projection and the housing.
The return arrangement for the intermediate plate may include at least one return projection which extends essentially radially outward and which engages in a return recess formed in the housing, the at least one return projection being displaceable in the direction of the axis of rotation and displaceable with a second circumferential direction movement play. At least one return force generating element is arranged between the at least one return projection and the housing for prestressing the at least one return projection and/or the at least one rotational coupling projection into a preferably essentially central position in the return recess or rotation coupling recess relative to the circumferential direction. The first circumferential direction movement play is preferably smaller than the second circumferential direction movement play.
Furthermore, at least one spring element which is preferably a tube spring element may be supported relative to the housing and to the return projection and arranged in each case on the two sides of the at least one return projection which are located in the circumferential direction.
A lifting force generating arrangement may be provided for generating a lifting force that prestresses the pressure plate toward the force accumulator. The lifting force generating arrangement ensures the separation of frictional surfaces bearing against one another when clutch disengagement operations are carried out.
When used in a multidisk clutch, the lifting force generating arrangement is then designed, furthermore, for generating a lifting force prestressing the pressure plate and the at least one intermediate plate axially away from one another.
Furthermore, in this case, the lifting force generating arrangement is designed for generating a force prestressing the at least one intermediate plate axially away from an abutment arrangement connectable or connected to the housing.
In a particularly simple and reliably acting way, the lifting force generating arrangement may include a first lifting spring arrangement arranged between the pressure plate and the at least one intermediate plate and a second lifting spring arrangement acting between the at least one intermediate plate and the abutment arrangement.
The construction space taken up by the pressure plate subassembly according to the present invention may be even further reduced in that the force accumulator comprises a diaphragm spring, this diaphragm spring then being arranged preferably essentially parallel to a bottom region of the bowl-like housing.
In the pressure plate subassembly according to the present invention, the housing may comprise a plurality of passage orifices for receiving of fastening elements, preferably screw bolts or the like, for attaching the pressure plate subassembly to the abutment arrangement.
To ensure that the radial dimension of the force accumulator may be designed essentially independently of the method of fastening the pressure plate subassembly to the abutment arrangement, a clearance may be provided in the force accumulator corresponding to the location of each passage orifice. The clearance on the force accumulator allows a respective fastening element to be introduced through the clearance and into the passage orifice.
Moreover, the force accumulator may be held on the housing by a plurality of holding elements.
In an alternative embodiment, the holding elements for holding the force accumulator onto the housing may be attached to the housing after the housing is attached to the abutment arrangement. This arrangement allows the largest possible force accumulator to be used.
In this embodiment, the holding elements may, for example, comprise holding screws, holding rivets or the like.
The passage orifices for the passage of the fastening elements are preferably arranged in a radially outer region of the housing. Furthermore, the radially outward extent of the force accumulator may be designed to correspond essentially to the radial extent of the housing.
The present invention relates to a friction clutch comprising a pressure plate subassembly according to the present invention connected to an abutment arrangement for joint rotation about an axis of rotation. The abutment arrangement preferably comprises a flywheel mass arrangement.
As already mentioned, this friction clutch is preferably a multidisk clutch.
The present invention relates to a method for assembling a friction clutch, comprising the steps of (a) attaching a pressure plate subassembly to an abutment arrangement, and (b) attaching a force accumulator to a housing of the pressure plate subassembly.
Step (a) may also comprise attaching the housing to the abutment arrangement via a plurality of fastening elements, preferably screw bolts or the like. Furthermore, step (b) may comprise attaching a force accumulator to an outer side of the housing via a plurality of holding elements.
According to an alternative embodiment, the method according to the present invention may comprise the following steps of (axe2x80x2) attaching a force accumulator to an outer side of a housing of a pressure plate subassembly, and (bxe2x80x2) attaching the pressure plate subassembly to an abutment arrangement. Step (bxe2x80x2) may comprise the attachment of the pressure plate subassembly to the abutment arrangement by guiding a plurality of fastening elements through passage orifices in the housing and through clearances in the force accumulator which correspond to the passage orifices.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.